高压旋喷桩与三轴搅拌桩组合加固杂填土地基监测数据分析

Monitoring Data Analysis of Combination of High⁃pressure Jet⁃grouting Piles and Triaxial Mixing Piles to Strengthen Miscellaneous Soil Foundation

以雄安站枢纽片区市政道路、综合管廊、排水管网系统(一期)工程为依托,对基坑围护桩外侧0.5m范围内进行高压旋喷桩坑外加固,在高压旋喷桩外侧4m范围内采用三轴搅拌桩加固,利用监测仪器分析基坑外侧杂填土地基加固前后桩水平位移、地基沉降位移和钢支撑轴力的变化。结果表明:一方面地基存在杂填土,桩间需考虑防水,加固杂填土地基用单一的高压旋喷桩方案或三轴搅拌桩方案很难达到预期的设计目标;另一方面杂填土地基加固前期土颗粒之间存在孔隙,导致沉降不完全,后期土体固结,土颗粒之间摩擦力增大,沉降趋于一个动态平衡。同时,围护桩和钢支撑在加固杂填土地基后仍存在不可恢复的残余变形。

Relying on engineering practice,the high⁃pressure jet grouting piles are reinforced outside the excavation within 0.5m of the outer side of the foundation excavation retaining piles.Three⁃axis mixing piles were used to reinforce the 4m outside of the foundation excavation,and the changes in the horizontal displacement of the pile,the settlement displacement of the foundation and the axial force of the steel support before and after the reinforcement of the miscellaneous fill ground outside the foundation excavation were analyzed.The analysis results show that:on the one hand,there is miscellaneous filling in the foundation,and waterproofing needs to be considered between the piles.It is difficult to achieve the expected design goals with a single high⁃pressure jet grouting pile scheme or a three⁃axis mixing pile scheme to strengthen the miscellaneous fill foundation.There are pores between the soil particles in the early stage of soil foundation reinforcement,which leads to incomplete settlement.In the later stage of soil consolidation,the friction between the soil particles increases,and the settlement tends to a dynamic equilibrium.At the same time,the retaining piles and steel supports still have irreversible residual deformations after reinforcing the miscellaneous fill foundation.